Device for manufacturing expanded material

ABSTRACT

A device is disclosed for producing expanded material using cutting rollers of special design, in which the individual annular cutting rings on the cutting rollers are provided with notches in their lateral surfaces, and when the cutting roller is viewed from above, these notches are seen to be trapezoidal in shape. The invention relates furthermore to the special configuration of the stretching system, wherein the strip-shaped non-stretched material passing through is gripped laterally by two toothed belts while at the same time the material to be stretched runs up, in its center section, on a recirculating element, such as a rounde-section belt running at an appropriate speed. This belt rises far enough out of the plane of the toothed belts that the desired transverse stretching of the material is achieved. By &#34;expanded material&#34; is meant a foil-like material, usually metal, in which a large number of parallel-oriented incisions are made, so that this material can then be pulled apart transversely to the direction of the incisions; as a result, the material is shortened in the longitudinal direction and the webs of material left between the incisions create a more or less three-dimensional lattice.

The present invention relates to a device expanded material from foil,in particular expanded metal from aluminium foil. The device comprises acutting unit for the continuous production of individual, discontinuousincisions in a foil, the cutting unit consisting of a cutting roller anda pressure roller, said device further comprising stretching means forexpanding the cut foil transversely to the longitudinal direction of thecuts.

Expanded metals are thin strips or foils, usually of metal, which, tostart with, are provided with a large number of discontinuous incisionsbefore being expanded, i.e. stretched, transversely to the longitudinaldirection of these incisions; the result is that the strips of metalwhich were previously located between the incisions are expanded to forma lattice structure. If this lattice is located in the same plane as waspreviously the metal foil in its starting condition, then the lattice isbroader and shorter than the foil in the starting situation relative tothe direction of the incisions in the foil, which is taken as thelongitudinal direction. In addition, metal strips which form the strutsof the lattice are located transverse to the plane of the lattice, sothat when the latter is viewed from above the struts appear in each caseonly in the thickness of the original metal foil. When the foil isformed into a lattice, the original longitudinal incisions are convertedinto mostly honeycomb-like or rhomboidal openings in the latter.

Although the device of the present invention described hereinafter canbe used to produce expanded material out of all thin materials, such asplastic, paper, wood and metal, in the following, only the conversion ofmetal foils into the generally known product "expanded metal" will beconsidered by way of example.

Such expanded metal is required for a wide variety of applications. Forexample, if expanded metal is used to provide an explosion-preventingsheath around naked flames, it is sufficient to manufacture it frommetal foils which are only a few hundredths of a millimeter thick. Whennon-metallic starting materials are used, the expanded material can beused as a filter, as a packaging material, as a carrier layer in theconstruction industry, and for many other purposes. On the other hand,it is possible in the same manner to produce a very stable expandedmetal from sheets up to several mm thick and this material can be used,for example, as a platform surface in scaffolding, as a step, orsimilar. Naturally, many other uses, for example as sieves, peelingknives, and other devices are conceivable.

Therefore to manufacture such expanded metal, it is necessary to usemachines which, to start with, are capable of making a large number ofdefined incisions, all having the same longitudinal orientation, in thinmetals, i.e. metal foils; next, these machines must pull the metal foilsapart transverse to the longitudinal direction of the incisions, thusmaking the metal wider, but also shorter and causing it to assume theshape of a honeycomb-like lattice.

Since continuous manufacturing processes are usually more economicalthan discontinuous processes, a decision was taken at a very early stageto use metal foils in the form of very long metal strips wound up onspools. These strips are provided with the required incisions as theypass between a cutting roller and a pressure roller.

If these incisions run in the longitudinal direction of the metal strip,subsequent expansion must be in the transverse direction of the strip,although the incisions may also be made transversely to the longitudinaldirection of the strip, so that the expansion must take place in thelongitudinal direction of the strip. Of course, a hybrid form isconceivable in which the incisions run obliquely to the longitudinaldirection of the foil strip. For the purpose of the followingexplanatory remarks, it is assumed that the incisions runlongitudinally, i.e. parallel to the longitudinal axis of the strip.

For this purpose, the two rollers are both cylindrical in shape andpossess a large number of annular grooves arranged around theircircumferential surfaces, between which similarly annular lands remain.In the cutting roller these lands act as cutting rings which, when theyenter the grooves of the pressure roller, cause incisions to be made atintervals in the metal foil interposed between the edge of the cuttingrings of the cutting roller and the edge of the lands on the pressureroller. In this way, when cutting rings with continuously rectangularcross section, i.e. straight cutting edges, are used, the original metalstrip is slit into a number of parallel, narrow metal strips which arenot joined with each other. In order to avoid this, the cutting edges onthe cutting rings of the cutting roller must be interrupted so that whenthe cutting rings enter the grooves on the cutting roller onlyindividual sections of the cutting edge slide along very close to theedges of the lands on the pressure roller, thus shearing the metal foil.In the intervening areas of the cutting rings of the cutting roller itmust be possible for the metal foil to be pressed by the lands of thecutting roller into the grooves on the drive roller, so that in theseareas the metal foil is not sheared.

As the cutting and pressure rollers continue to rotate and the lands andgrooves of the two rollers move apart from each other once more, the cutmetal foil should not become jammed in the grooves of the pressureroller, but instead must run smoothly out of the grooves without anyadditional tearing occurring in the metal webs of the cut metal foil.

In the past, attempts have been made to solve this problem by arrangingguide brushes and similar devices between the cutting roller and thepressure roller, although this measure usually did not provide optimalresults because the metal webs often became caught up in the rectangularrecesses in the cutting rings of the cutting rollers, which are neededto interrupt the cutting process at the cutting rings. Once thecontinuous cutting of the metal foils was complete, it was necessary tocontinuously stretch the cut foils transversely, at the same timeshortening them in the longitudinal direction. To accomplish this,attempts were made to seize the edges of the foil strip emerging fromthe cutting unit and to transport it onwards, while at the same timestretching it in the transverse direction by ensuring that thesegripping devices did not run parallel but moved apart; alternatively,the stretching was brought about by arranging a movable or immovableobstacle projecting at an angle upwards from the plane of the foil andarranged between the gripping devices at the edge of the foil; whilebeing transported longitudinally, the metal foil was forced to run uponto this obstacle so that the straight and short transverse connectionbetween the edges of the metal foil ceased to exist and in this way, orby a combination of both methods, the metal foil was stretchedtransversely to the longitudinal direction. When this obstacle was ofthe immovable type, it usually took the form of a nose-shaped ramp.However, in this case friction was generated between the ramp and themetal foil, so that frequently deformation or tearing of the metal stripwas caused, or no stretching took place because the material was tornout of the lateral guides.

In addition, it was no longer possible to satisfactorily solve theproblem of gripping the edges of the metal foil because, for example,the edge zone of the foil strip tore off or it slipped out of thelateral engagement between the conveyor chains. For this purpose, in thepast it has been the practise to arrange two Reinolds conveyor chains inclose contact with each other, one above and one below the metal foil,gripping the latter and transporting it in the longitudinal direction.

Apart from the fact that such Reinolds conveyor chains are relativelyexpensive, they were exposed to a considerable amount of wear, whichresulted in frequent interruptions of the operation of the stretchingunit in order to replace these chains; and, furthermore, the metal foilswere frequently not adequately held by these chains because the metalfoil was either damaged by the Reinolds conveyor chains or the gripbetween the chains was not firm enough to permit stretching in atransverse direction because the metal foil was simply pulled out of thetwo chains.

It is therefore the task of the invention to make available a device formanufacturing expanded material which operates smoothly andsatisfactorily, and which in particular avoids the aforementioneddisadvantages of the state of the art technology.

This task is solved by making improvements to the cutting unit as wellas to the stretching unit.

The cuts in the metal foil, which are generated by the cutting edges ofthe cutting rings on the cutting roller, are usually interrupted byadopting the following design: The circumferential surface of thecutting roller is provided not only with a large number of grooves ofessentially rectangular cross section, but also the cutting rings orlands left standing between these grooves each possess two flanks which,together with the circumferential surface of the cutting roller, formthe two cutting edges of each cutting ring. These cutting edges must beinterrupted in order to avoid making a continuous incision in thelongitudinal direction of the metal foil, and instead to make a largenumber of individual, interrupted outs. For this purpose, recesses areincorporated into the flanks of the cutting rings and these recessesextend into the area of the circumferential surface of the cuttingroller, i.e. of the cutting ring, and thus form a notch in thiscircumferential surface which interrupts the cutting edge.

Normally, the cutting rollers are not made from a one-piece cylinder butare manufactured by assembling together a number of thin discs ofalternatingly large and small diameter on a common shaft arrangedconcentrically to the axis of rotation of the cutting roller, so thatthe individual discs form alternatingly the cutting rings or the bottomsof the interlying grooves. The recesses in the flanks of the cuttingrings are usually produced by milling recesses in the flanks of thediscs forming the cutting rings, and these recesses are of such a shapethat the notch produced in the circumferential surface of the cuttingring is rectangular in cross section. In the case of cutting rollersmade from one piece, the recesses are produced by erosion machining.Therefore, this always resulted in damage to the metal foil, or the foileven became wrapped around the cutting roller or the pressure roller.Brushes, guide plates and other devices used to facilitate the removalof the cut metal strip from the cutting unit were for the most partineffective.

In the system according to the invention, the recesses in the flanks ofthe cutting rings are for this reason differently shaped, namely in sucha manner that their cross section; i.e. the notch visible in theciroumferential surface of the cutting ring, is not rectangular in shapebut of trapezoidal cross section, with the base of the trapezium lyingon the extended line of the cutting edge. When a notch of this shape isused, the cut metal strip does not become caught up or jammed in thecutting roller. It has been found advantageous to give the sides of thetrapezoidal notch an angle of 40°-75°, and most advantageously 45°,relative to the base. The cut foil emerges smoothly from such a cuttingroller, regardless of whether the latter is of one-piece construction ormade from individual discs forming the cutting rings and the bases ofthe grooves. To provide support, guide elements are additionallyinstalled in the area of the cutting unit, e.g. wires arranged close tothe foil, both above and below it, and running parallel to thelongitudinal direction of the foil, i.e. they run horizontally throughthe grooves of the cutting and pressure rollers. Similarly, lining thegrooves of the cutting roller and possibly of the pressure roller up toa certain level with elastic material, such as rubber, which wasintended to force the cut metal foil out of the grooves, proved to be ofincidental benefit.

On the other hand, it proved advantageous to fill the grooves of thepressure roller partially with such an elastic material, because in thisway it is possible to avoid the adhesion of the foil in the grooves ofthe drive roller, although the adhesion is much less pronounced than inthe grooves of a cutting roller designed according to the current stateof the art.

Furthermore, the present invention also relates to improvements in thestretching unit by means of which the cut, strip-shaped material, whichneed not be metal but may be made for example of plastic foil, isexpanded transversely to the longitudinal direction, which automaticallyresults in a shortening of the strip or of the incisions in thelongitudinal direction. Compared with the state of the art, in which theout metal strip is gripped at its edges and transported onwards, whileat its centre it is forced to run over a ramp projecting upwards at anacute angle from the plane of the cut metal strip, the followingimprovements have proved to be advantageous:

To start with, instead of a ramp structure, a recirculating, essentiallyone-piece belt is selected having preferentially a round cross section.This belt consists preferentially of a material possessing relativelyhigh friction in relation to the material of the cut strip, so that ifthis recirculating belt has a higher speed than the running speed of themetal strip, the latter is drawn upwards in its centre section by thisrecirculating belt, because of the good grip existing between the metalstrip and the belt. However, as a rule, every effort should be made toadjust the speed of the belt to the speed of the foil, because this isthe best way to avoid distorting or damaging the foil.

The lateral grip on the strip-shaped out foil has also been improved. Inthe state of the art equipment the foil is gripped preferentially byReinolds conveyor chains, i.e. link chains having specially shaped linksmade from hard plastic. These Reinolds conveyor chains are expensive andbecause of the hardness of the material they are subject to higher wearthan a flexible, more adaptable material, and in addition, when acontact pressure adequate to grip the foil is used, it is very easy forthe foil to be damaged or for it to tear at the edges.

In the process according to the invention, instead of such conveyorchains toothed belts are used, and at least the surface of such belts ismade of rubber or a rubber-like, relatively elastic material, and theteeth of the toothed belt point outwards so that the foil is gripped atthe edges between the lower strand of the toothed belt running above thefoil, and the upper strand of a toothed belt running below the foil, andit is transported forwards in this manner; the toothed belts runparallel over a certain distance to permit the teeth and gaps in thetoothed belts to mesh with each other. It has proved advantageous to usein particular a woven toothed belt made of a plastic-textile mixture. Ofcourse, the shape of the tooth on the toothed belt must be selected insuch a manner that the shape of the teeth corresponds as closely aspossible to the shape of the gaps. Furthermore, by providing adequatetensioning of the toothed belts, or also by mechanically supporting thebelts for example by using supporting devices over which the meshingstrands of the toothed belts run, the opposing pressure between the twobelts can be set in such a way that it is strong enough to hold thefoil.

This method of laterally gripping the out metal foil between toothedbelts offers, however, one additional and highly decisive advantage overthe Reinolds conveyor belts, which are substantially flat at theirpoints of contact with the metal foils:

When expanding the cut, strip-shaped metal foil transversely to thelongitudinal direction, not only is the foil made wider but in thelongitudinal direction it becomes shorter; consequently, in acontinuously operating device, with cutting and stretching unitsarranged in tandem and joined by the metal foil, steps must be taken toensure that during the stretching process the running speed of themetallic foil is reduced in accordance with the shortening of the stripwhich takes place when it is stretched. A foil which is gripped by twointermeshing toothed belts must follow the zig-zag path of the teeth andthe gaps between the teeth, therefore over a certain length of thetoothed belt a larger length of strip-shaped foil, depending on theheight of the teeth on the toothed belt, is gripped. Therefore, astrip-shaped foil emerging at a speed V from the cutting unit can begripped by a toothed belt running at a lower speed V2 without causingany tension, or on the other hand without causing any back-up in thestrip-shaped, cut material. When an appropriate choice of tooth shape,i.e. tooth height and tooth spacing, is made for the toothed belt, it ispossible to compensate in this manner for the shortening of the foil inthe longitudinal direction, so that at the emergence from the stretchingunit, i.e. at the end of the intermeshing toothed belts, the speed ofthe finished expanded metal, as dictated by the shortening of the foilin the longitudinal direction, is the same as the speed of the toothedbelts, and thus corresponds to the speed of the material emerging fromthe stretching unit.

When using gripping and transporting devices which lie flat on the foil,the speeds of these gripping and transporting devices are logically thesame as that of the material being processed, either at the inlet of orthe outlet from the stretching unit, or at any point in between, but themachinery does not reduce the speed at which the strip-shaped materialbeing processed runs through the system.

Advantageous embodiments of the invention are described in more detailin the following, with reference to the accompanying simplifieddiagrammatic drawings, which show:

FIG. 1: a perspective view of the cutting roller and stretching units,arranged in tandem;

FIG. 2: a developed view of the circumferential surface of the cuttingroller;

FIG. 2A: a view similar to that of FIG. 2 but showing a modifiedembodiment of the part shown;

FIG. 3: a cross-sectional view through the cutting and pressure rollersalong the section A--A in FIGS. 1 and 2, wherein the cutting roller andthe pressure roller do not mesh with each other, as is customary when inoperation, but are shown for the sake of clarity at a distance from eachother;

FIG. 3A: a view similar to that of FIG. 3 but showing a modifiedembodiment of the part shown;

FIG. 4: a top plan view of the stretching unit, with the foil to bestretched, as in FIG. 1, just entering the stretching unit; and

FIG. 5: of FIG. 2.

Throughout the drawings, the corresponding parts are referred to withthe same reference numbers. When needed, a plurality of the same partsof the structure is referred to with the corresponding numeralsdistinguished from each other by a letter.

FIG. 1 shows a tandem arrangement of a cutting unit 2 and a stretchingunit 3, and it is indicated that as the foil runs continuously throughthese two units they must be arranged one behind the other, but notimmediately so, because it is possible to interpose further facilities,for example a counter, control devices, alignment and deflectiondevices.

Both the cutting unit 2 and the stretching unit 3 may be mounted on acommon base frame, as indicated by the number 6, or they can be mountedat different points and on different base frames, depending on therequirements of the production operation.

The position and mutual alignment of the various units depends on theposition and direction of motion of the foil which is being processed;in the embodiment illustrated, the foil is running horizontally fromleft to right. Therefore, the cutting unit 2 consists of a pressureroller 5 and a cutting roller 4 which are arranged horizontally oneabove the other and intermesh with each other, and make a large numberof individual incisions 7 oriented in a longitudinal direction in thefoil 1 running between them. The cutting roller 4 and the pressureroller 5 are mounted on both sides in bearing blocks 19 which are inturn mounted on the base frame 6, and they are driven by drive unitssuch as electric motors, which are not shown here.

In the cutting unit 2 shown here, the pressure roller 5 is arrangedabove the cutting roller 4, but the arrangement could equally well bereversed. The circumferential surface of the cylindrical cutting roller4 is provided with a large number of substantially annular grooves 8,between which substantially annular cutting rings 10 project. In adeveloped view, the circumferential surfaces 14 of these cutting rings10 exhibit a zig-zag structure, which can be better recognised in FIG.2. This derives from the fact that the circumferential surface 9 of thecutting roller 4 contains not only a large number of said annulargrooves 8 having a substantially rectangular cross section, withsimilarly annular cutting rings 10 disposed therebetween and orientedconcentrically to the axis of rotation of the cutting roller 4.Furthermore, recesses 12 are incorporated into the flanks 15 of thesecutting rings 10. The recesses 12 extend into the circumferentialsurface 14 of the cutting rings 10 to form notches 13 in the annularcircumferential surfaces 14 of the cutting rings 10, so that theoriginally annular shape of the circumferential surfaces 14 of thecutting rings 10 is changed by lateral notches. As a result, the cuttingedges 11 are also interrupted, without the notches 13 they would have acontinuously annular shape. This makes it possible to produceindividual, discontinuous incisions 1 in the longitudinal direction oftransportation 38 (FIG. 4) of the strip-shaped foil 1. In the presentcase (see FIGS. 1 and 2), in each case only one cutting edge 11 of eachcutting ring 10 is interrupted by notches 13. The cutting edges 11,interrupted by notches 13, of two adjacent cutting rings 10 are turnedtowards each other.

The cutting rings 10 are so wide that they fit exactly in the equallyannular grooves 18 provided in the circumferential surface 9 of thepressure roller 5, so that when the cutting unit 2 is operating, thecutting rings 10 of the cutting roller 4 project partially into thegrooves 18 of the pressure roller 5, and likewise the lands projectingbetween the grooves 18 on the pressure roller 5 engage partially in thegrooves 8 of the cutting roller. As a result, as the cutting roller 4and the pressure roller 5 both rotate and the strip-shaped metal foilruns between them, the foil 1 is sheared between the cutting edges 11 ofthe cutting roller and the oppositely acting edges of the lands on thepressure roller. The foil 1, which is provided in this way with a largenumber of individual cuts 7 arranged in the longitudinal direction 38 oftransport and offset in relation to each other, runs either immediately,or after the interposing of additional units, into the stretching unit 3where it is expanded transversely to the longitudinal direction oftransport 38. The stretching unit 3 consists of two intermeshing toothedbelts 30 in the area of the edges 34 of the foil 1. In each case, one ofthe toothed belts 30 is arranged above or below the foil 1 and is guidedover at least two rollers 31 in such a manner that the lower strand ofthe upper toothed belt 30 and the upper strand of the lower toothed belt30 each run parallel to the foil 1 and also parallel to the othertoothed belt 30. Since the toothing on the toothed belt is selected insuch a way that the size of the teeth 32 corresponds to the size of thegaps 33 between the teeth, the lower strand of the upper toothed belt 30and the upper strand of the lower toothed belt 30 mesh with each otherbecause of their outward oriented teeth 32 and because of theappropriate selection of the spacing between the upper and lower rollers31. The rollers 31 ensure adequate tensioning of the toothed belts 30 sothat an adequately high contact pressure is exerted by the toothed belts30 over the entire length of their intermeshing sections, therebygripping the edges 34 of the foil 1 and not only transporting it in thelongitudinal direction of transport, but also gripping the foil firmlytransversely to the longitudinal direction of transport 38 in order tobring about the desired stretching in this transverse direction.

The stretching is carried out by means of the following arrangement:When the stretching unit 3 is viewed from above, as shown in FIG. 4, abelt 35 is seen running approximately in the middle between and parallelto the toothed belts 30, and this belt passes over at least two rollers31, whose plane 36 of rotation runs approximately in the longitudinaldirection 38 of transport of the foil 1, but perpendicular to the planeof the foil 1. The upper strand 39 of this belt 35 runs obliquelyupwards from below the plane of the foil 1 so that it forms an acuteangle 40 (FIG. 1) with the longitudinal direction 38 of transport, andthis angle corresponds preferentially to a gradient of 1:2 to 1:4,preferably 1:3, between the upper strand 39 and the plane of the foil 1.The angle of said gradient is coincident with a plane which is alsoreferred to as "a longitudinal plane generally perpendicular to areference plane, said reference plane being a generally planar sectionformed by that part of the foil which is gripped between said toothedbelts". The rollers 31, by means of which this belt 35 is tensioned, arealso in turn positioned in bearing blocks 19 which are mounted on thebase frame 6 Similarly, this belt 35 is also driven by drive units,preferentially electric motors, in such a manner that the upper strand39 of the belt 35 moves obliquely upwards to the right, i.e. in thedirection of motion of the foil 1.

If, now, when the stretching unit 3 is operated, the foil is gripped atits edges 34 by the pairs of toothed belts 30 and transported forwardsin the longitudinal direction of transport 38, then the foil 1 runs uponto the upper strand 39 (also referred to as "foil engaging strand") ofthe belt 35 and the foil 1 is thereby stretched transversely to thelongitudinal direction of transport as the gradient of the upper strandof belt 35 increases; the latter belt is preferentially round in crosssection and has a diameter in the order of 25 mm. In order to permit thefoil to run up smoothly on the belt 35, the speed of the belt 35 shouldat least correspond to that of the toothed order to guarantee adequatefriction and thus driving force between the belt 35 and the material ofthe foil which is to be cut.

When selecting the toothed belt 30, it is advisable to ensure that notonly the tooth profile guarantees that the teeth 32 and the gaps betweenthe teeth 33 of the toothed belts 30 intermesh, but also the hardness ofthe material from which the toothed belt is made must be carefullyselected to guarantee that adequate gripping force is exerted on foil 1.It has been found that the most advantageous choice of rubber toothedbelts is one having a Shore hardness of about 60.

When this choice of parameters is made, the device for producingexpanded material can be used without any problems to cut and stretch,for example, aluminium foils between 3/100 mm and 12/100 mm thick.

Of course, in order to achieve this and to guarantee continuousinteraction of the cutting unit 2 and the stretching unit 3, the speedof rotation of the toothed belts 30 as well as of belt 35 (also referredto as "a stretching belt") must be matched to the speed of rotation ofthe cutting roller 4 and the pressure roller 5. Because of the foldingof the foil 1 around the teeth of the toothed belts 30, the speed ofrotation of the toothed belts 30 is lower than the speed of thearriving, cut foil 1, but the amount by which the speed is reduceddepends on the spacing and height of the teeth 32 on the toothed belt30.

Both in the right half of FIG. 1 as well as in FIG. 4, the foil 1 isdepicted solely up to the start of the stretching unit 3, so as not toimpair the depiction of the other parts of the device.

Furthermore, FIGS. 2 and 3 contain detailed depictions of the cuttingroller 4. FIG. 2 shows a developed view of the circumferential surface 9of the cutting roller 4, or more precisely the circumferential surface14 of the cutting rings 10 of the cutting roller 4 which are leftbetween the grooves 8, the latter being arranged annularly andconcentrically to the axis of rotation of the cutting roller 4; thesegrooves 8 have a preferably rectangular cross section, as can best beseen in FIG. 3.

These cutting rings 10 each possess two flanks which together with thecircumferential surfaces 14 of the cutting rings 10 form the annularcutting edges 11 and these, in conjunction with the flanks of thegrooves 18 of the pressure roller 5, cause the foil 1 to be sheared.However, for this purpose, the cutting roller 4 and the pressure roller5 must be arranged so closely together that grooves 8 or 18 as well asthe interlying lands of the two rollers partially mesh with one another.In contrast, the cutting roller 4 and the pressure roller 5 are shownspatially separated in FIG. 3 in order to simplify the depiction andidentification of the individual surfaces and edges.

The notches 13 in the circumferential surfaces 14 of the cutting roller1, which are visible in FIG. 2, are formed by the recesses of which onlyone recess 12A is visible in FIG. 3. As mentioned above these recessesalso project as far as the circumferential surface 14 of the cuttingrings 10 and thus form the notches 13.

As far as the effect on the foil 1 is concerned, the main factor is theshape of the notch 13, as shown in FIG. 2, and not so much theconfiguration of the recess 12 in the lower portion of the flanks 15 inFIG. 3.

The shape of the recesses 12 shown in FIG. 3 is preferentially obtainedwhen, as shown in FIG. 3A, the cutting roller 4 consists of individualdiscs of alternatingly large and small diameter, which are joinedtogether one after another in an axial direction to form the cuttingroller 4. Before the discs are assembled, the aforementioned recesses 12are provided in the flanks 15 of the discs which later form the cuttingrings 10, and this is done by means of a milling cutter so that thebottom of the recesses 12 in the lower region of the flanks 15 has anarcuate configuration. However, these recesses 12 can also be preparedin another manner, which is required mainly when the cutting roller 4 isnot made up of individual discs but is produced form a singlecylindrical piece. This embodiment is shown in FIG. 3.

Similarly, in FIG. 3, which depicts a cross sectional view along thelines A--A in FIGS. 1 and 2, it can be seen that the grooves 18 of thepressure roller 5 are partially filled with rubber 17 which iscompressed by the action of the cutting rings 10 as the foil 1 is beingcut; subsequently, the rubber expands again to its original shape,thereby forcing out the foil which is partially located in the groove18.

In the state of the art equipment, on the other hand, it was necessaryto put rubber or other elastic material in the grooves 8 of the cuttingroller 4 in order to force the foil 1 out of these grooves 8, becausethe foil 1 often became caught up in the recesses 12 of the cuttingrings 10, so that when it emerged from the cutting unit 2, additional,unintended tears occurred in the foil 1, often causing breaks incross-connecting pieces or even tearing the entire foil 1, so that itwas not possible to further process it into expanded metal. Such faultsare particularly disruptive during continuous operations because, if anyfaults also occur in the functioning of the stretching unit 3, the wholeinstallation frequently has to be shut down or a high reject rate isincurred.

The hooking of the foil 1 in the recesses 12 seems to be due to the factthat, in the state of the art equipment the notches created by therecesses 12 in the circumferential surfaces 14 were rectangular in crosssection

In contrast, in the method according to the invention, these recesses 12are designed in such a way that their cross section, and thus the notch13 in the circumferential surface 14 of the cutting rings 10, istrapezoidal in shape, and the base of the trapezium lies along theextended line of the cutting edges 11. The sides 41 of these trapezoidalnotches are arranged preferentially at the same angle 43 ofpreferentially 40° to 75°, and in particular 45° relative to the base 42of the trapezium, as shown in FIG. 5.

As a result of this inclination of the sides of the recesses 12, thefoil 1 runs so smoothly and without tearing from the cutting unit thatboth the elastic inlays in the grooves 8 of the cutting roller 4, aswell as the stripping brushes and other types of guide fitted at theexit from the cutting unit, and also the rubber inserts in the cuttingrollers, need only be fitted as further optional refinements.

Those skilled in the art will appreciate that many modifications of theembodiment described above may be carried out without departing from thepresent invention. Accordingly, I wish to protect by letters patentgranted on this application all such embodiments as properly fall withinthe scope of my contribution to the art.

The embodiments of the invention in which an exclusive right orprivilege is claimed are defined as follows:
 1. A device formanufacturing expanded material from foil, in particular expanded metalfrom aluminum foil, comprising a cutting unit to continuously produceindividual, discontinuous cuts in the foil, the cutting unit includes acylindrical cutting roller and a pressure roller and a stretching unitfor expanding the cut foil transversely to the longitudinal direction ofthe cuts, wherein grooves (8) are provided in the cylindrical cuttingroller (4) and the cylindrical pressure roller (5) includes grooves (18)arranged annularly in the circumferential surfaces of the cutting roller(4) and the pressure roller (5).
 2. A device according to claim 1,wherein the grooves (18) are filled at least partially with an elasticmaterial.
 3. A device according to claim 1, wherein the belt (35) ismade of one of either rubber or PVC.
 4. A device for manufacturingexpanded material from foil, in particular expanded metal from aluminumfoil, comprising a cutting unit for the continuous production ofindividual, discontinuous incisions in a foil, wherein the cutting unitincludes a cutting roller and a pressure roller, and a stretching unitfor expanding the cut foil transversely to the longitudinal direction ofthe cuts, wherein:a) in the cutting unit (2), the cutting roller (4) isessentially cylindrical in shape and possesses a large number of grooves(8) of a generally rectangular cross section in a circumferentialsurface (9) of the cutting roller (4), so that lands forming cuttingrings (10) having flanks are left standing between the grooves (8), b)the flanks (15) of the cutting ribs (10) possess several recesses (12)which extend into the circumferential surface (14) of the cutting ring(10), the recesses of the flanks of two adjacent rings which forms anyone of said grooves being located in an alternating position so that, atany point of the periphery of the respective groove, there is a recessin only one of the two flanks whereby only one of respective two opposedcutting edges (11) of the cutting ring (10) is interrupted by a recess(12), c) the recesses (12) are shaped in such a way that trapezoidallyshaped notches are formed in the circumferentaial surface (14) of thecutting ring (10), and d) the cylindrical pressure roller (5) similarlypossesses a large number of annular grooves (18) whose quantity anddimensions are matched to the grooves (8) of the cutting roller (4) sothat through the intermeshing of the grooves (8, 18) and the lands ofthe cutting and pressure rollers (4) and (5), the foil passing betweenthem is cut.
 5. A device according to claim 1, wherein the notches aredefined by a pair of sides enclosing an angle of 40° to 75°, and inparticular 45°.
 6. A device according to claim 1, wherein the notchesare defined by sides which enclose angles of equal size.
 7. A deviceaccording to claim 1, including guide wires strung above and below andin the longitudinal direction of the foil (1), and located in thegrooves of the cutting roller (4) or the pressure roller (5).
 8. Adevice for producing expanded material from foil, in particular expandedmetal from an aluminum foil, comprising a cutting unit to continuouslyproduce individual discontinuous cuts in a foil, the cutting unitincluding a cutting roller, a pressure roller, and a stretching unit forexpanding the cut foil transversely to the longitudinal direction of thecuts, and wherein:a) the stretching unit (3) possesses two pairs oftoothed belts (30) which grip the two edges (34) of the foil (1) andtransport the latter in a longitudinal direction; one toothed belt (3)runs above and the other below each edge (34) of the foil (1) in thesame plane perpendicular to the foil (1), which the teeth (32) orientedoutwards, so that the upper and lower toothed belts (30) respectivelyrun parallel to each other over a certain distance, thereby permittingtheir teeth (32) and the gaps between their teeth (33) to intermesh andthus gripping in each case an edge of the foil (1) between them andtransporting the foil longitudinally, b) at least one belt (35) fortransversely stretching the foil, said at least one belt circulatingaround at least two rollers (31) in a plane perpendicular to the planeof the foil (1) and in the longitudinal direction of transport (38), alength (39) of the belt (35) rising at an acute angle (40) relative tothe longitudinal direction of transport (38) from below the plane of thefoil (1) and the speed of the belt (35) being at least greater than orthe same as that of the arriving foil (1).
 9. A device according toclaim 8, wherein the belt (35) is of round cross section and has adiameter of approximately 33 mm.
 10. A device according to claim 8,characterized by the fact that the belt (35) runs at a speedcorresponding to the speed of arrival of the foil (1).
 11. A deviceaccording to claim 8, wherein the belt (35) is made of a material havinghigh coefficient of friction relative to the material of the foil.
 12. Adevice according to claim 8, wherein the toothed belts (3) possestrapezoidal teeth and the associated spaces (33) between the teethcorrespond in shape and size to the teeth (32).
 13. A device accordingto claim 8, wherein the tooth belts (30) are made of rubber having aShore hardness of 50-70.
 14. A device according to claim 8, wherein thefoil (1) is transversely stretched in the stretching unit (3)preferentially by a factor of 1.3 to 2.0.